Maybe you've seen the proliferation of rainbow icons and profile pictures around the 'net after the historic marriage equality ruling in the United States and want to join the fun. Or maybe you're planning a pride event and want to make some themed images for promotion. Maybe you just love rainbows! Whatever the case, this tutorial will have you putting rainbows on everything in no time.

1. Collect Your Images

You'll need two images for this tutorial: a base image that you want to give the rainbow treatment, and a rainbow. I've included a 2000-pixel rainbow flag image file with this tutorial.

Here's the base image I'll use to demonstrate. It's a picture of me, a simple headshot that I use on a few social media accounts and in our company directory here at Tuts+.

I'm ready for the treatment

All kinds of images are suitable for a rainbow overlay but simple graphic compositions tend to work best.

2. Prepare the Base Image

In this step you'll get your base image ready for the rainbow overlay treatment.

First, open your base image in Photoshop (Control-O). Then resize the image (Control-Alt-I) to your desired final output size. In theory you could resize the image later, but I like to work at the output size so that I get an accurate representation of what the end-product will look like all along the way.

Now that your image is the right size, convert it to black and white. Add a Black & WhiteAdjustment Layer (Layer > New Adjustment Layer > Black & White). Adjust the sliders in the resulting dialogue box to create a black and white conversion that is to your liking.

3. Bring the Rainbow

Now open the rainbow image in Photoshop. Using the Move Tool (V), click-and-hold the flag image, then drag and drop it onto your base image. Alternatively, SelectAll (Control-A), Copy (Control-C), and Paste (Control-V) the rainbow image onto the base image.

Depending on your image the rainbow might be too large or too small. Use the Free Transform (Control-T) tool to change the size of the layer so that it matches your base image.

Next change the Blending Mode of the rainbow layer to Hard Light and reduce the layer Opacity until it looks right to you. In my case, that was 50%. Some images might also work with Soft Light instead.

Almost there

4. Bring Back Image Detail

Now, you could stop there, but let's take it one step further. Looking at the example above you can see that the base image looks a little bit washed out. Let's bring back some of the detail in the image.

Select your base image and Duplicate (Control-J) it. Drag the duplicate layer to the top of the layer stack.

Next duplicate the Black & White Adjustment Layer. Drag it above the duplicate base image. Holding Alt, click the line between the adjustment layer and the duplicate base layer so that the adjustment only applies to the layer directly below.

Next, change the blending mode of the duplicate base layer to Multiply and reduce the layer Opacity to 50%.

Almost there, but still a little something missing

5. Bring Back Contrast

In this, the final step, you'll bring back the contrast lost when you added the detail layer.

Create a new Curves Adjustment Layer (Layer > New Adjustment Layer > Curves). Click to add points, then give the curve a nice S-shape, like so:

The s-curve pushes the highlight values higher and the shadow values lower, creating a higher-contrast image. Adjust the points on the curve until you are happy with the image. You can also reduce the Opacity of the layer for fine control.

If you like a slightly less saturated rainbow you can apply the curve to the detail layer instead of the entire image. Hold Alt and click the line between the Curves layer and the layer below it. That's what I've done with my image.

Here is the final result:

Full rainbow, all the way

I like my image with a lot of rainbow, but if you'd prefer a more subtle effect you can reduce the Opacity of the rainbow layer and increase it for the detail overlay layer. Here's a version with 30% and 70% Opacity, respectively:

Conclusion

So, to recap, here are the main steps in this tutorial:

Collect you images. Simple and graphic compositions work best.

Resize and convert the base image to black and white.

Bring in the rainbow image and size it to the base image.

Bring back image detail.

Bring back contrast.

The key part of this tutorial is playing with the combination of Blending Mode and Opacity. Each image requires a slightly different approach, but with Adjustment Layers and fine control you should be able to produce the kind of rainbow images you'd like.